Getting ActiveRecord (Rails) to_xml to use xsi:nil and xsi:type instead of nil and type
The default behavior of XML serialization (to_xml) for ActiveRecord objects will emit 'type' and 'nil' attributes that are similar to XML Schema Instance attributes, but aren't 开发者_开发技巧set in a XML Namespace.
For example, a model might produce an output like this:
<user>
<username nil="true" />
<first-name type="string">Name</first-name>
</user>
Is there anyway to get to_xml to utilize the XML Schema Instance namespace and prefix the attributes and the values?
Using the above example, I'd like to produce the following:
<user xmlns:xsi="http://www.w3.org/1999/XMLSchema-instance" xmlns:xs="http://www.w3.org/1999/XMLSchema">
<username xsi:nil="true" />
<first-name xsi:type="xs:string">Name</first-name>
</user>
I had similar requirements and chose to subclass ::Builder::XmlMarkup instead:
require 'builder/xmlmarkup'
class MyXmlMarkup < ::Builder::XmlMarkup
def tag!(sym, *args, &block)
if @level == 0 # Root element
args << {"xmlns" => "http://my_company.com/api/schemas/xml",
"xmlns:xsi" => "http://www.w3.org/2001/XMLSchema-instance"}
end
if args[:nil] = true
args << {"xsi:nil" => true}
end
super(sym, *args, &block)
end
end
then you can use it with:
foo.to_xml(builder: MyXmlMarkup.new(indent: 2))
I ran into something similar, but when calling #to_xml on a Hash, not on an AR instance.
I came up with this helper:
#
# Returns a new Builder::XmlMarkup that'll handle API's to_xml needs
# Usually you don't need to construct a builder, as to_xml will create one
# however we need some things modified (adding a namespace, XSD-nillable-compliant-nils
# and to_xml is too braindead to allow us to alter such behaviors externally
#
def api_new_xml_builder
builder = Builder::XmlMarkup.new(:indent => 2)
class << builder
def method_missing(*args, &block)
@api_seen ||= 0
@api_seen += 1
if @api_seen == 1
# Root element. Needs some decoration
args[1] ||= {}
args[1]["xmlns"] = "http://my_company.com/api/schemas/xml"
args[1]["xmlns:xsi"] = "http://www.w3.org/2001/XMLSchema-instance"
end
if args[2].is_a?(Hash) && args[2][:nil] == true
args[2]["xsi:nil"] = true
end
super(*args, &block)
end
end
builder
end
It's then used like so:
builder = api_new_xml_builder
foo.to_xml(:builder => builder)
Note that I opted to keep the existing nil= and type= attributes, and add my own xsi-prefixed nil, however it's trivial to replace them instead.
精彩评论